From the star-studded cast of superheroes so big they can't even all fit on a movie poster to the budget - Wall Street Journal estimates it ties Justice League and Pirates of the Caribbean: At World's End as the second-most expensive film ever made - and the scale of the planet-destroying villain Thanos.

And of course the stakes couldn't be any higher. If Thanos gains possession of all six infinity stones then he has the power to control space, time and the very fabric of the universe.

Directors Anthony and Joe Russo had a formidable task of bringing together the plot lines of the past 10 years of Marvel blockbusters.

The size of this film is both its greatest asset and its greatest stumbling block (it runs for a whopping 149 minutes).

It's nice to see so many beloved characters coming together, whether it's reunions such as Black Widow and Bruce Banner or heroes meeting for the first time such as Thor's hilarious introduction to the Guardians of the Galaxy.

Thor, Rocket and a teenage Groot go off on their own mission.Marvel

With so much time and space to cover, though, there isn't much time for all that mushy stuff.

Our heroes are soon split up across the universe in the hopes of defending the infinity stones Thanos is yet to acquire. The story deftly jumps back and forth as the Avengers, Guardians and other heroes are either battling Thanos or his goons.

More of a distant, looming threat in the previous Marvel films, Thanos (played by Josh Brolin) is finally fleshed out in the few moments when he's not wreaking havoc.

A very big and angry Thanos.Marvel

The purple Titan explains his reasons for wanting to wipe out half the population of the universe and he almost makes case for sustainability and population control. Of course, he nominated himself for the job and that doesn't sit well with all us rational folk.

The film goes to some dark places as the good guys face impossible choices. Could you muster the will power to kill the one you love if it saved half the lives in the universe? It's a major gear change from the more light-hearted adventures in Thor: Ragnarok and Guardians of the Galaxy Vol 2.

The body count in Infinity War is high - on both sides. The Russo brothers understand that without real losses it doesn't really feel like the fate of the entire universe is on the line.

Those casualties, which I would dare not spoil, give Infinity War a wonderful unpredictability you don't often find in action blockbusters.

Spider-Man and Iron Man team up with the Guardians of the Galaxy.Marvel

Sure there's comfort in knowing the good guys are going to win, but haven't we already seen that countless times on the big screen?

What happens if the heroes sacrifice everything and it's still not enough?

When the credits roll on Infinity War, you'll wonder 'where does Marvel go from here?'"

Of course this isn't the end, with another Ant-Man movie, Captain Marvel and an untitled Avengers film, again with the Russo brothers directing, all in the works. There's even a third Guardians film in development for release in 2020.

The possibilities of where Marvel's Cinematic Unvierse will go are more exciting than ever.